The invention is concerned with a shield assembly in or for use in a mine roof support and more particularly but not essentially to a shield assembly comprising at least one prop and a canopy adapted to lie against the roof as well as a base plate adapted to lie on the floor which are connected through a hinged shield construction which has one or more hinge axes lying in the longitudinal direction of the face, wherein the shield construction transfers at least in part the support forces between the roof and floor.
A shield assembly of this kind is known for example from the Journal "GLUCKAUF" 103 (1967) pages 1013 to 1017. A particular characteristic of such a shield support assembly is that the support forces of the prop or props or the hinged shield construction are spread out, in scissors fashion, so that the hinges of the shield construction are included in the force flow for development of the support forces. The shield support assembly of the stated art differs basically from those support blocks or advancing roof supports which are provided on the goaf, or rear, side i.e., the side away from the working face, with flushing shield plates or flushing shield boxes, which are not included in the force flow for development of the support forces but serve only the purpose of preventing penetration of the waste into the face space.
In the known shield assemblies of the said kind on so far unexplained grounds deformations and breakages frequently occur in the hinge parts of the shield construction. As a basis for these defects it was at first supposed that the hinges of the shield construction had not been sufficiently stable. As careful research has shown the above-mentioned defects in the hinges of the shield construction are in no way to be traced back to the fact that these hinges were too weakly constructed but could be traced back to the fact that these hinges were unfavourably loaded. In fact these unfavourable loadings result when relative movements between roof and floor in the longitudinal direction of the face occur or when irregularities in the floor or roof are present. With such loadings strong transverse forces arise in the hinge mechanism of the shield construction which distort and damage these hinges.
It is therefore an object of the present invention to improve the shield support assembly in such a way that the overloading phenomena and damages referred to are avoided in the hinges of the shield construction.